ABSTRACT: Coming to believe that the Bible is God’s word does not require extensive historical evidence, as helpful as that can be. The best defense for the Bible’s trustworthiness is in the pages of the Bible itself. From the early church on, Christians have recognized that the Bible’s authority is “self-authenticating,” meaning that Scripture bears certain qualities within itself that testify to its divine origins. One of the most powerful of these qualities is the unity and harmony of Scripture: the books of the Bible are consistent within themselves, with prior revelation, and with the overall story of the Bible.

Few qualities are more central to the health of the church — and to the spiritual condition of the individual believer — than a robust commitment to the authority and inspiration of Scripture. As Paul reminded Timothy, “The sacred writings . . . are able to make you wise for salvation through faith in Christ Jesus” (2 Timothy 3:15). And of course, Jesus himself clearly testified to the centrality of the word: “Man shall not live by bread alone, but by every word that comes from the mouth of God” (Matthew 4:4; cf. Deuteronomy 8:3).

Even so, having an orthodox doctrine of Scripture is one thing; being able to defend that doctrine against attacks is quite another. When asked why we believe the Bible is God’s word — perhaps the most common question about the Bible in our current cultural moment — Christians need to have some sort of answer. Yet this is precisely the place where many Christians lock up. Since they have been convinced that the only respectable answer is a near-exhaustive catalog of the historical evidences for the Bible’s authenticity, and since they have not studied (nor probably ever will study) such evidence, they are often left with no answer. All that can be done is to refer the skeptic to the experts and hope for the best.

At this point, however, we should remember that historical evidences are not the only way we know the Bible is from God. Indeed, Christians throughout history have typically appealed to another way that is not only more accessible, but, in some ways, also more fitting for a book that claims to be God’s word. Christians have argued that the Bible is self-authenticating, meaning that it bears certain internal qualities or attributes that show that it is from God.¹ Put bluntly, we can know the Bible is the word of God from the Bible itself.

A Self-Authenticating Bible

While the idea of a self-authenticating Bible sounds strange to modern ears, that was not the case within the early centuries of the faith, when apologetics was a necessary part of survival in the hostile Greco-Roman world. Although the earliest Christians used a variety of arguments to defend the Bible’s inspiration (such as proof from fulfilled prophecy), they were keen to acknowledge that the Bible was its own best proof. Clement of Alexandria, for example, regarded the Scripture as the equivalent of a philosophical “first principle” and thereby able to authenticate itself.² Clement argued that those who have faith hear the “voice of God” in the Scriptures, which operates as a “demonstration that cannot be impugned.”³ And again, he insists that the “voice of the Lord . . . is the surest of all demonstrations.”⁴

Clement’s self-authenticating approach flowed naturally from his theological conviction that the Scripture, as the very voice of God, was the ultimate authority. When it comes to demonstrating the truth of an ultimate authority, one cannot help but appeal to it. Indeed, if one tried to prove an ultimate authority by appealing to some other authority, then that would just prove it wasn’t really ultimate. Thus, ultimate authorities, by definition, must be self-authenticating. This is why, when God swore an oath, he “swore by himself” (Hebrews 6:13).

Clement was not alone. Origen articulates this self-authenticating approach even more clearly:

If anyone ponders over the prophetic sayings . . . it is certain that in the very act of reading and diligently studying them his mind and feelings will be touched by a divine breath and he will recognize the words he is reading are not utterances of man but the language of God.⁵

Elsewhere, Origen insists that Old Testament prophets “are sufficient to produce faith in any one who reads them.”⁶ Incredibly, according to Origen, simply reading (or hearing) the Bible puts a person in touch with its divine qualities. If that person has the help of the Spirit — what Origen calls “a divine breath” — then he will see those qualities for what they are, the very words of God himself.

Indeed, merely reading the Bible, and apprehending its divine qualities, is how the pagan philosopher Tatian was converted to Christianity. On a quest to “discover the truth,” he describes how he came to believe Scripture was from God:

I was led to put faith in these [Scriptures] by the unpretending cast of the language, the inartificial character of the writers, the foreknowledge displayed of future events, the excellent quality of the precepts. . . . And, my soul being taught of God, I discern that the former class of [pagan] writings lead to condemnation, but that these [Scriptures] put an end to the slavery that is in the world.⁷

This patristic backdrop explains why the Reformers were also committed to a self-authenticating approach to Scripture. Not surprisingly, Calvin led the way,⁸ but he was followed by William Whitaker⁹ and John Owen.¹⁰ And later Reformed thinkers followed suit, including Francis Turretin,¹¹ Jonathan Edwards,¹² and Herman Bavinck.¹³

The Unity and Harmony of Scripture

So, if the Bible bears certain divine qualities or attributes that show it is from God, then what exactly are these qualities? Typically, theologians have pointed to three: (a) the beauty and excellency of Scripture, (b) the power and efficacy of Scripture, and (c) the unity and harmony of Scripture. Indeed, the Westminster Confession of Faith points to these three in its discussion of how Scripture “doth abundantly evidence itself” to be the word of God (WCF 1.5).

Even so, there is little doubt that this third quality — Scripture’s unity and harmony — has played the most dominant role in authenticating books, both in early Christianity as well as in the modern day. To say the Scripture has unity and harmony is to affirm that any scriptural book is (a) consistent within itself (i.e., it has no internal contradictions), (b) consistent with prior revelation (i.e., it is orthodox), and (c) consistent with the overall story of the Bible. Let’s briefly examine each of these aspects.

Consistent with Itself

The earliest Christians recognized that divine books, because they are from God, cannot contradict themselves. After all, God cannot lie (Titus 1:2). Justin Martyr affirms this fundamental principle: “I am entirely convinced that no Scripture contradicts another [Scripture].”¹⁴ Irenaeus agrees: “All Scripture, which has been given to us by God, shall be found by us perfectly consistent.”¹⁵ Theophilus is no different: “All the prophets spoke harmoniously and in agreement with one another.”¹⁶ Tertullian is quite blunt: “And here I might now make a stand, and contend that a work ought not to be recognized . . . which exhibits no consistency.”¹⁷

Since humans, ordinarily, are fallible creatures who are prone to error, finding such remarkable internal consistency in a book can be seen as evidence for that book’s divine origins. Not only is this true for single books (e.g., the Gospel of Luke), but it is particularly true when the Bible is viewed as a completed whole. How could humans achieve absolute consistency across 66 different books, written by almost 40 different authors, over thousands of years, and on different continents? Only a divine author could do that.

Consistent with Prior Revelation

We could also explore the theme of consistency in terms of the doctrine that any given book teaches. Is that doctrine faithful to the truths that have been revealed in prior stages of divine revelation? In the Old Testament, a prophet’s words were tested by comparing them to prior revelation (Deuteronomy 18:20), and in the New Testament we see the Bereans comparing Paul’s teaching to Scripture (Acts 17:10–12). When we speak of a book’s doctrinal consistency, we are simply arguing that a book has to be orthodox in order for it to be from God.

However, one might wonder whether Christians had a standard for orthodoxy before the New Testament canon was completed. Was there a way that orthodoxy could be determined? Absolutely. For one, early Christians tested books by comparing them to the Old Testament. This was the doctrinal foundation for the apostles, as well as for Jesus himself. But early Christians also tested a book’s orthodoxy by comparing it to the “rule of faith.” The rule of faith was basically a brief summary of apostolic teaching that allowed Christians to succinctly and clearly state the essence of what they believed — an early creedal statement, of sorts. The rule of faith should not be viewed as new revelation, or extrabiblical teaching, but basically a summary of the Scripture’s own story line. Armed with both the Old Testament and the rule of faith, Christians were able to assess — accurately and clearly — whether a book was orthodox.

Of course, we should remember that while all scriptural books are orthodox, not all orthodox books are Scripture. A book could be orthodox and yet not part of the canon. For this reason, orthodoxy was typically used as a negative criterion. In other words, it was the lack of orthodoxy — and the positive presence of heresy — in a book that allowed Christians to know that it must not be from God. A good example is how our earliest canonical list, known as the Muratorian fragment, rejected the forged epistle of Paul to the Laodiceans on the grounds that it contained “Marcionite heresy” and “it is not fitting that poison should be mixed with honey.”

Consistent with the Overall Story of the Bible

Christians believed (and still believe) that the Bible not only consists of 66 separate books, all with distinct stories, but essentially functions as a single unified book with one overarching story of redemption. Thus, when early Christians were evaluating whether a book should be received as Scripture, they were concerned not only with whether it matched doctrinally, but with whether it completed the Old Testament story. The Old Testament is like a book without a final chapter, like a play without a final act. And Christians were busy looking for its proper conclusion.

A number of New Testament books demonstrate this redemptive-historical connection plainly. For example, consider the fact that Matthew, the first book in the New Testament canon, begins with a genealogy. For most Westerners, this means little — indeed, it is often skipped. But for a Jew, this would have meant everything. It was Matthew’s signal that the story of Jesus completed the story that began in the Old Testament with Abraham. In other words, Matthew doesn’t just tell the story of Jesus; he tells the story of Jesus in light of the story of Israel. Jesus is the climax of the Old Testament narrative.

This fact is confirmed when we remember that the last book of the Old Testament in Jesus’s day would have been the book of Chronicles (the books were in a different order than in our present Bibles). And the book of Chronicles begins with a genealogy. Thus, the last book of the Old Testament and the first book of the New Testament would have both begun with genealogies focused on David! This led D. Moody Smith to declare, “Matthew makes clear that Jesus represents the restoration of that [David’s] dynasty and therefore the history of Israel and the history of salvation. Thus, Jesus continues the biblical narrative.”¹⁸

The redemptive-historical character of New Testament writings is seen more plainly when they are compared to apocryphal writings, particularly apocryphal gospels. Notably lacking in most apocryphal gospels is a definitive link to the Old Testament story of Israel. Indeed, some apocryphal gospels, like the Gospel of Thomas, are not even stories at all, but just collections of sayings of Jesus. Gospels like this were rejected precisely because they could not reasonably be viewed as a fitting sequel to the Old Testament narrative.

Reading the Bible as one unified story also provides the opportunity for the reader to draw links between its various parts. It is noteworthy, for example, that Jesus recapitulates the story of the exodus, functioning as a new Moses who, like the first Moses, was almost killed at birth (Matthew 2:13–15; Exodus 2:1–2), delivers the law on a mountain (Matthew 5:1; Exodus 19:1–25), brings bread from heaven (John 6:32; Exodus 16:4), has power over the sea (Mark 4:35–41; Exodus 14:21), and provides a Passover lamb for the sins of the people (John 1:29; Exodus 12:1–7). Such connections cause us to marvel at how remarkably unified all the Scripture really is. And it makes us recognize, again, that no human could have possibly orchestrated such a vast web of subtle, profound, and eye-opening links like we find in Scripture.

In many ways, then, the collective impression given by all the books of the Bible, when read as a whole unit, speaks to their divine origins. We are reminded that the Bible has a synergistic quality about it — you get something when all the books are read together that you don’t necessarily get when they are read individualistically. It is like the “fifth voice” in a barbershop quartet; you don’t hear it until all the voices are joined together.

Implications of a Self-Authenticating Bible

We have argued that the remarkable unity and harmony of Scripture is one of the main qualities of Scripture that demonstrates its divine origins. And of course, there are other qualities as well that we have not explored here. What are some of the implications of this reality for our ministries and for the average believer?

First, it reminds us that every believer can know the Bible is God’s word without having to become an expert in biblical archaeology, ancient manuscripts, or other kinds of historical evidences. That’s not to suggest these issues are unimportant (they are very helpful in their own way); it’s just that they are not necessary for a person to know the Bible is from God. Unfortunately, many believers are convinced they are necessary, leaving them personally in doubt about the truth of God’s word and having to rely on the experts who have studied such matters. But if the Bible really bears these internal qualities, then all Christians can, with the help of the Holy Spirit, know it is divinely inspired. Remember, even the pagan philosopher Tatian came to believe in the truth of the Scriptures merely by reading them.

Second, the self-authenticating nature of Scripture should reshape our thinking about the best way to convince the skeptic of the truth of the Scriptures. If the Bible bears these internal qualities, then the best way to demonstrate those qualities is to faithfully teach it and preach it, or to invite the non-Christian to read it. We need to unleash the Bible and let it do what it was designed to do: powerfully display God’s glory. Thus, we would do well to heed the well-known advice of C.H. Spurgeon:

Suppose a number of persons were to take it into their heads that they had to defend a lion, full-grown king of beasts! There he is in the cage, and here come all the soldiers of the army to fight for him. Well, I should suggest to them . . . they should kindly stand back, and open the door, and let the lion out! I believe that would be the best way of defending him, for he would take care of himself; and the best ‘apology’ for the gospel is to let the gospel out.¹⁹